Multiplex telegraph system



Nov. 16 1926. 1,606,937

H. H. HARRISON MULTIPLEX TELEGRAPH SYSTEM Filed Oct. 22. 1925 2 Sneets-Shee. 1

a I l l l I I I Nov. 16 1926.

M 3 qr-" 3% I F-O I I IMF z,- flzrgfflef $2771 Iran Patented Nov. 16, 1926.

UNITED STATES PATENT OFFICE.

HARRY HUGHES HARRISON, F LIVERPOOL, ENGLAND, ASSIGNOR TO AUTOMATIC TELEPHONE MANUFACTURING COMPANY LIMITED, OF LIVERPOOL, ENGLAND.

MULTIPLEX TELEGRAPH SYSTEM.

Application filed October 22, 1923, Serial No. 670,113, and in Great Britain October 28, 1922.

The present invention concerns improvements in or relating to telegraph systems and more particularly concerns an arrangement' for overcoming the disadvantages of high speed single channel working with Morse code. The chief of these disadvantages is the inability of automatically and selectively routing trafiic at points where the line diverges or at intermediate points en route. This flexibility is a great advantage of multiplex systems but up to the present it has not been employed in high capacity systems using the land line Morse code. Owing to the present tendency to extend cables to a group of oflices remote from the cable head, automatic routing of trafiic has become highly desirable so that retransmission is avoided at the cable station which thereby functions simply as a repeater station and also as the point where cable testing and the adjustment of the duplex balance are undertaken;

Previous attempts at developing a multiplex system using the land line Morse code have been unsuccessful, in that they have tended to give a distorted signal and to increase the time required for the transmission of a message.

The object of the present invention is to provide a multiplex system using the land line Morse code in which the distortion of signals is eliminated and in which the speed of working is substantially equal to that at present attained in high capacity systems sages are sent over different channels instead of over one channel only. Thus in the case of a cable having a one way 3 eed of 90 words per minute, either three c annels at words or two channels at words per minute could be arranged for.

According to one feature of the invention, this object is attained in a multiplex system using a code with signal units of unequal length by arranging for the line time to be divided equally among the diiferent channels durin periods of time equal to the longest period of which the duration of the individual signal units forming the code are exact multiples, so that each signal unit comprises an integral number of components.

Thus in the case of the land line Morse code the period which is divided among the various channels is the length of a dot, since a dash is as long as three dots.

with the additional advantage that the mes-- One way of effecting this is by the provision of two synchronous devices at the transmitting and receiving ends respectively so as to connect up the corresponding transmitting and receiving apparatus of the various channels successively, the receiving apparatus including a polarized relay having cations may be made in the constructional" details without departing from the spirit of the invention.

In the drawings, Fig. 1 is a diagram showing how for two channel working with land line Morse code, half of each signal element is suppressed, and Fig. 2 showshow the two sets of signals are combined for transmission over the line. F ig. 3 shows diagrammatically the general arrangements at the sending station for two channel working, while Fig. 4 shows the corresponding arrangements at the receiving end. Fig. 5 shows an alternative driving arrangement for securing synchronism at the sending and receiving ends.

Considering Fig. 1 more in detail, time is represented in a horizontal direction and the dotted lines divide the diagram into units such as are used for sending over each channel, a represents a Morse signal for the letter L, for sending over the first channel, while 6 represents a second Morse signal (i. e. the letter F), which is to be sent overthe second channel. The lines 0 and J, from which ordinates above the line represent positive currents and those below the negative currents, represent the actual polarity and duration of the currents sent over the line in respect of each signal.

It will be apparent from Fig. 1 that in the case of two channel working, the first channel has the second half of each signal component. suppressed, while the second channel similarly has the first half so pressed. For three channel working clear y only one-third of each signal component is actually operative for each channel, and sim-' ilarly for larger numbers of channels. Fig. 2, which represents the combination of c and d, Fig. 1, on a single base, shows the resultant current which would flow over the line;

In the sending equipment shown in Fig.

"3, T and T are transmitters preferably of the keyboardperforator orfsimilar type, for instance similar to that described in my book' Printing Telegraph Systems and Mechanisms on pp. 175 and 176. SWV and SW are the corresponding star wheels which are rigidly fixed to the shaft carrying the contact brush arm CBA of the rotary distributor. This shaft is driven by a. phonic wheel or other suitable synchronous motor which is not shown.

The contact brush arm CBA is arranged to sweep over two contact rings, one of which R is solid while the other R- is' divided up into a number of insulated segments. The length of these segments is such that for two channel working four of them occupy an angle equal to the pitch of the star wheels. Alternate segments are connected together and the two groups are connected through the normally closed contacts of the synchronizing, switch SS to the respective transmitter keys.

The solid ringiof the distributor is connected to the polarized transmitting relay TR the armature of which in its operated position connects positive battery to the line The upper winding of GR is a correcting winding and is traversed by. a momentary current each time the line relay LR reverses, the fiow of continuous current being prevented by the condenser c The speed of vibration may be adjusted by varying the values of the resistances F, r and of the condenser 0 By this means the phonic wheel may be regulated b the signals re-. ceived so that a perfect pliase relationship between the transmitting and receiving distributors mag be obtained. The synchronizing switch S provided for'adjusting purposesat the transmitting station, is adapted when operated to connect the two groups of segments of the divided ring to positive and negative battery respectively. The transmitting relay TR responds accordingly and connects, positive and negative current alternately over the line, whereupon the line relay LR vibrates and sets the Gulstad relay GR in operation. The adjustment of the length.

that it will reverse its armature an auxiliary circuits is then effected in known PR PR", which control receiving apparatus RA, RA corresponding to the two' channels. comprise recorders, receiving perforators or the like but is shown in the drawing as a printer of the Creed type and is illustrated in my book as above mentioned on page The polarized relays PR and PR have no neutral position so that when they are operated by a current flowing in one direction This receiving apparatus may.

they will remain in theoperated position and F in Fig. 1, will now be followed through in detail. When transmitters T and T which operate in synchronism, are

displaced to send the dot signal which at this point is to be sent over both channels, relay TR is operated in the circuit from battery B, transmitter T ring R a segment,

contact brush arm CBA, ring R relay TR,

earth. Relay TR thereupon operates and connects positive battery over the line L to line relay LR (Fig 4). A circuit is thereby completed by the armature of line relay LR from positive battery, ring R", contact brush arm 'CBA, ring R*, a segment, polarized relay PR earth. The armature of relay PR is therefore operated to control the recording apparatus RA When. the contact brush arm CBA reaches the adjoining 1) segment, relays TR and LR will be maintained operated but now current is connected over a b segment. of the receiving rotary distributor to relay PR so that the recording apparatus RA is operated. It should be noted that as relay PR has no neutral position it will remain in the operated position. andthus the recording .appa'ratus will receive a signal of full dot When the next segment is swept over by the contact brush arm, negative current will flow through the transmitting relay TR so connect negative current over the line. Relays LR and PR are therefore restored to normal and hence the recording apparatus HA is no longer operated. Similarly during the next half dot when a 5 segment in encountered HA is restored to normal. The succeeding operation will be readily followed: PR receives three operating impulses and is then reversed and is subsequently operated once and restored; thus a dash and a dot are sent. In the same time a dot and a dash are 'sent overthe second channel so that PR is operated accordingly.

It will thus be seen that the signals transmitted over the various channels fit into one another for transmission over the line and are then resolved into their components at the receiving end. This method clearly permits the most eficient utilization of line time while securing the advantages of multiplex working with the land line Morse code.

In Fig. 5 is shown a modification of the transmitting apparatus which does away with the necessity for having the star wheels on the same shaft as the contact brush arm are rigidly connected. These ratchet wheels have twice as many teeth as the star wheels and thus are driven at the same rate as the rotary distributor. Obviously now, the transmitters and star wheels may be controlled from the transmitting distributor,

over a single wire;

What I claim is:

1. A multiplex telegraph system comprising a plurality of automatic transmitting devices, circuit closing means controlled by .said devices and adapted to be operated for unequal periods of time to transmit different signal elements, a transmitting relay, a

distributor, inter-connecting arrangements between said transmitting devices and said distributor for securing the connection of said devices successively to said relay during periods of time equal to the longest period of which all the signal elements are exact multiples; a telegraph line connected at one end to contacts of said transmitting relay,"

a line relay connected to the other end of said line, a plurality of receiving devices corresponding in number to the number of transmitting devices and a seconddistributor controlled so as to have a movement corresponding to that of said first distribu-' tor to enable said line relay to control said receiving devices in accordance with the sigtimes the length of the signal element for thefdot signal comprising a plurality of automatic transmitting devices, circuit cl0s ing means controlled by said devices and adapted to be operated for unequal periods of time to transmit either dots or dashes, a transmitting relay, a distributor, interconnecting arrangements between said transmitting devices and said distributor for securing the connection of said devices successively to said relay during periods of time equal to the length of the dot signal, a

telegraph line connected at one end tocon tacts of said transmitting relay, a line relay connected to the other end of saidline, a

plurality of receiving devices corresponding in number to the number of transmitting devices and a second distributor controlled so as to have a movement corresponding to that of said first distributor to enable said line relay to control" said receiving devices in accordance with the signals transmitted from the corresponding transmitting devices;

3. A multiplex telegraph system comprising a plurality of automatic transmitting devices, circuit closing means controlled by daid devices and adapted to be operated for unequal periods of time to transmit different signal elements, a telegraph line, a distributor at the transmitting end of saidline, inter-connecting arrangements between said transmitting devices and said distributor for securing the division of the line time equally between said transmitting devices durin periods of time equal to the longest period of which. all'the signal elements areexact .multiples, a plurality of receiving devicesing contacts of said line relay to said reeivmg devlces 1n correspondence wlth the con- 1 nection of said transmitting devices to said line, said receiving devices being adapted to take up a new position only in response to a modification 10f current transmitted to the line by the corresponding transmitting device. y

A multiplex telegraph system comprising a plurality of automatic transmitting devices, circuit closing means controlled by said devices and adapted to be operated for "unequal periods of time to transmit different signal elements, a transmitting relay, a' distributor, inter-connecting. arrangements between said transmitting devices and said distributor for securing the connection. of

said devices successively to said relay during periods of time equal'to the longest period of which all the signal elements are exact multiples, a telegaph line connected at one end r6 to contacts of said transmitting relay, a line relay connected to the other end of said line, a plurality of two-position polarized relays corresponding in number to the num ber of said transmitting devices and adapted to remain in either position until moved to the opposite position by a reversal of cur rent in their windings and asecond distributor controlled so as to have a movement corresponding to that of said first distributor to enable said line relay to control said polarized relays to be operated to one position in accordance with the operation of said circuit closing means.

5. In combination, for use in a multiplex telegraph system, a plurality ;of automatic mit-ting relay, a distributor, inter-connecting arrangements between said transmitting devices and said distributor for securing. the connection of said devices successively to said relay during periods of time equal to the longest period of which all the signal elements are exact multiples, and a cable connected to contacts of said transmitting rela 6. In combination for use in a multiplex telegraph system employing a code with signal elements of unequal length, a cable, a line relay adapted to be operated over said .cable, contacts controlled by said line relay, a plurality of receiving devices adapted to take up a new position only in response to a change of position of said linerelay con-' tacts When said contacts are connected thereto, a distributor, circuitconnections between "conneeting arrangements between said driv-- ing means and said line relay contacts for controlling the speed of said distributor so that fsaid line relay contacts are connected successively to said receiving devices-V during periods of time equal to the longest period of which all the signal units are exact mu1-' tipleS.

Signed by me at Liverpool, England, this of October; 1923.

5th da I IAR-RY HUGHES HARRISON. 

